125×235-26×235+235 、 238×99、 2+4+6+8···+80 、 2000-3-6-9···-5
来源:学生作业帮 编辑:作业帮 分类:数学作业 时间:2024/05/16 07:46:34
125×235-26×235+235 、 238×99、 2+4+6+8···+80 、 2000-3-6-9···-51-54 ,它们的简便计算!
125×235-26×235+235
=235×(125-26+1)
=235×100
=23500
238×99
=238×(100-1)
=238×100-238
=23800-238
=23562
2+4+6+8···+80
=(2+80)×40÷2
=82×40÷2
=1640
2000-3-6-9
=2000-(3+6+9+……+54)
=2000-[(3+54)×18÷2]
=2000-[57×9]
=2000-513
=1487
=235×(125-26+1)
=235×100
=23500
238×99
=238×(100-1)
=238×100-238
=23800-238
=23562
2+4+6+8···+80
=(2+80)×40÷2
=82×40÷2
=1640
2000-3-6-9
=2000-(3+6+9+……+54)
=2000-[(3+54)×18÷2]
=2000-[57×9]
=2000-513
=1487
125×235-26×235+235 、 238×99、 2+4+6+8···+80 、 2000-3-6-9···-5
125×235-26×235+235 238×99 2+4+6+8···+80 2000-3-6-9···-51-54
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